1. Field of the Invention
The present invention relates to the technical field of display panels and, more particularly, to a display and backlight controller and a display system using the same.
2. Description of Related Art
Liquid crystal display (LCD) devices are widely used as space-saving type displays and, in recent years, have begun to be used in electronic devices. However, due to the limited battery power of the electronic devices, a low power LCD is anxiously demanded to avoid charging the battery frequently.
When a still image is displayed on the screen, it basically doesn't need to refresh the still image so often. Therefore, it is possible to drive the panel in a low frequency driving mode and this leads to the realization of low power LCD. However, in case of the low frequency driving mode, it is likely to observe an unsatisfactory flickering phenomenon. FIG. 1 is a schematic view illustrating one of the factors which would result in the flickering phenomenon. As shown in FIG. 1, in the low frequency driving mode, the refresh rate is about 1 Hz; i.e., the display system updates a still image in every second. The flexoelectric effect becomes an issue if the refresh rate is low, as indicated in circle “A” of FIG. 1. A large change of brightness results in the flickering phenomenon.
To prevent the flickering phenomenon, LCDs are usually driven with a high frequency (about 60 Hz) as shown in FIG. 2. FIG. 2 is a schematic view illustrating the brightness in a normal driving mode in the prior art. As shown in FIG. 2, in the normal driving mode, 60 frames are displayed per second. That is, the time for displaying a frame is about 16.67 milliseconds (ms). In the normal driving mode, the brightness change is not so obvious due to the high driving frequency. However, in consideration of displaying a still image, it wastes much power for refreshing 60 frames per second.
In addition to the flexoelectric effect, the brightness of the TFT panel may also be changed due to TFT cut-off current leakage. In this case, the brightness will be gradually changed during a suspend period. FIG. 3 is a schematic view illustrating the brightness change in low frequency driving mode of TFT LCD in the prior art. As shown in FIG. 3, the brightness is expected to be maintained with a constant value in the suspend period. However, due to the TFT cut-off current leakage, the brightness is gradually decreased in actual application. Especially, in the end of the suspend period, the brightness is decreased dramatically. At the next charge period, the capacitors corresponding to the pixels of the TFT panel are charged again, and then the brightness of the TFT panel is abruptly increased, resulting in the undesired flickering phenomenon.
Therefore, it is desirable to provide an improved display panel system to mitigate and/or obviate the aforementioned problems.